1. Field of the Invention:
The present invention relates to a radio receiver and particularly to a radio receiver containing a cassette tape deck therein.
2. Description of the Related Art:
Many car or domestic radio receivers include a cassette tape deck contained therein so that a user can easily play back cassette tapes in addition to radio broadcastings. Recently, multi-functional radio receivers have been developed. For example, a radio receiving system has been now developed which has a radio broadcasting interrupt function for offering a radio broadcast announcing traffic or emergency information during the playing-back of a tape, if necessary. This is accomplished by transmitting broadcasting waves containing an interrupt signal which is multiplexed with general broadcasting waves and by receiving and demodulating them into the desired radio broadcast, in accordance with an FM multiplex broadcasting technique such as RDS.
FIG. 2 is a block diagram illustrating the primary parts of a radio receiver with a tape deck which is constructed in accordance with the related art. The radio receiver comprises a tape deck 11 which is adapted to detect the insertion of a cassette tape (not shown) thereinto and to be actuated by electric power supplied from a (TAPE+B) terminal 12 to the tape deck 11 through a transistor 13. The collector of the transistor 13 is connected with a drive motor 14 and plunger 15 in the tape deck 11. The plunger 15 is connected with a head drive mechanism 16 which in turn is connected with a head 17. On powering on, a head holding latch (not shown) in the head drive mechanism 16 is actuated to hold the head 17 in contact with the tape. Playback signals outputted from the head 17 are fed to a radio/tape output switching circuit 22 through an equalizer circuit 21 and then outputted from a speaker 24 through an amplifying circuit 23.
The emitter of the transistor 13 is connected with the (TAPE+B) terminal 12 through a drive resistor 26 while the base thereof is connected to the emitter through a resistor 29 and also to the collector of a transistor 28 through a drive resistor 27.
The emitter of the transistor 28 is grounded with the base thereof being grounded through a resistor 31. The base of the transistor 28 is also connected with the interrupt signal output terminal of a microcomputer 34. The interrupt signal outputted from the interrupt signal output terminal is a negative logic (active "L") signal which is inputted to the base of the transistor 28 and also to the radio/tape output switching circuit 22. The radio/tape output switching circuit 22 selects either the cassette tape signal or the radio reception signal, depending on the logical level of the interrupt signal 33.
In the apparatus, the radio receiver further comprises a radio receiving circuit 37 which includes various conventional circuits such as a high-frequency amplifier, a local oscillator, a mixer, an intermediate frequency amplifier, a detector, a noise killer, a multiplexer and so on. The radio receiving circuit 37 provides radio waves containing FM broadcast signals and the like received by an antenna 38 to the radio/tape output switching circuit 22 and at the same time feeds data multiplexed with the FM broadcast signals to a data demodulating circuit 39. The data demodulating circuit 39 demodulates the data, the demodulated data being outputted therefrom to the microcomputer 34.
On operation, the electric power is applied to the transistor 13 through the (TAPE+B) terminal 12 when a cassette tape is inserted into the tape deck 11 through its tape inlet (not shown). Since at this time, the active "L" interrupt signal 33 from the microcomputer 34 is in a "H" state in the tape signal prefered mode, the transistors 28 and 13 are also turned on to energize the drive motor and plunger 14, 15. At the same time as the drive motor 14 is actuated, the head holding latch of the head drive mechanism 16 is actuated to bring the head 17 into contact with the tape. Tape voice signals read out from the cassette tape are supplied to the radio/tape output switching circuit 22 through the equalizer circuit 21.
When the radio/tape output switching circuit 22 senses the tape voice preferential mode "H" in the interrupt signal 33, the circuit 22 selects the tape voice signals from the equalizer circuit 21 which in turn are outputted therefrom to the amplifying circuit 23 to drive the speaker 24.
If the traffic or emergency information signals multiplexed with the FM broadcasting signals are received during such a playback of tape voice signals, these multiplexed signals are demodulated by the data demodulating circuit 39 after being received by the radio receiving circuit 37 through the antenna 38. The demodulated signals are received by the microcomputer 34 which in turn changes the interrupt signal 33 from "H" to "L". Thus, the transistors 28 and 13 are turned off to shut off the power to the drive motor and plunger 14, 15. At the same time as the drive motor 14 is stopped, the head drive mechanism 16 is unlatched to move the head 17 away from the tape.
As the interrupt signal 33 is changed to "L", the system is switched from the tape voice prefered mode to the radio voice prefered mode. In other words, the radio/tape output switching circuit 22 selects the radio receiving circuit 37 to cause the received traffic or emergency information signals to be output through the speaker.
On termination of the transmission of traffic or emergency information signals, this is sensed by the microcomputer 34 which changes the interrupt signal 33 back to "H" so that the tape voice prefered mode will be selected.
FIGS. 3 and 4 illustrate the relationship between tape, capstan and pinch roller in the tape desk 11. In the tape voice prefered mode, the head holding latch of the head drive mechanism 16 (FIG. 1) is held by the plunger 15 (FIG. 1) such that the tape 43 is nipped between the pinch roller 41 and the capstan 42, as shown in FIG. 3. This will be referred to as the "pinching-on state".
In the radio voice prefered mode, the tape 43 is released between the pinch roller 41 and the capstan 42 as shown in FIG. 4 since the plunger 15 is deenergized. This will be referred to as the "pinching-off state".
In the related art radio receiver with the tape deck, thus, both the drive motor and plunger 14, 15 are deenergized when the system is shifted to the radio voice prefered mode due to the interrupt caused by traffic or emergency information signals. If the traffic or emergency information signals are unstably received by the radio receiver in a bad radio wave reception area such as between mountains, the interrupt signal 33 from the microcomputer 34 will be frequently changed from "H" to "L" or vice versa. Thus, the plunger 15 will be frequently energized and deenergized. This results in frequent repetition of the pinching-on and pinching-off states. As a result, mechanical noise will be undesirably generated and the tape will eventually be damaged.
It is therefore an object of the present invention to provide an improved radio receiver with tape deck which can prevent the occurrence of undesirable mechanical noise and also tape damage due to the frequent switching between the radio and tape prefered modes.